1. Field of the Invention
The present invention relates to a wire cleaning device for cleaning a charging wire in a corona discharger used in a copying machine, a facsimile transmitter/receiver, a printer, or the like.
2. Prior Art
Corona dischargers for use in electrophotographic copying machines or the like have corona charging wires. If the corona charging wire is smeared or dirty, then a corona discharge generated thereby becomes irregular. Where a corona discharger is employed as a charge unit in an image forming device in a copying machine or the like, a corona discharge irregularity causes a charging irregularity which results in a white line on a copied image. In case a corona discharger is used as an image transfer unit in an image forming device, a corona discharge irregularity produces an image transfer failure (appearing as a white patch). Where a corona discharger is employed as a sheet separator in an image forming device, a corona discharge irregularity tends to cause a recording sheet separation failure. To prevent these problems from occurring, it is current practice to employ a wire cleaning device for cleaning a charging wire in a corona discharger. The wire cleaning device includes a cleaning means such as a pad or the like which is reciprocally moved by a motor to clean the charging wire. The cleaning means moves from a home position at one end of the charging wire to the other end thereof. When the cleaning means engages a stopper at the other end of the charging wire, an overcurrent flows through the motor. When the cleaning means moves back to the home position and is stopped there, an overcurrent flows again through the motor. By detecting such an overcurrent flowing through the motor, it can be detected that the cleaning means has moved from the home position to the other end of the charging wire for reversing the motor, and also that the cleaning means has returned from the other end of the charging wire to the home position for de-energizing the motor. One cycle of cleaning operation is finished upon completion of one reciprocating movement of the cleaning means.
Since fine particles called toner are employed in the image developing unit in the image forming device, the cleaning means is smeared with more toner and more load is imposed on the cleaning means as it is used in more cleaning cycles. Toner scattered from the image developing unit may be deposited o the charging wire to the point where the load on the cleaning means will stop the cleaning means during a cleaning process. When this happens, the motor is heated to break the charging wire, resulting in an improperly reproduced image or a sheet jam. The movement of the cleaning means from the home position to the other end of the charging wire and back is detected by an overcurrent flowing through the motor, as described above. Even if the cleaning means is locked for some reason somewhere between the home position and the other end of the charging wire, an overcurrent flows through the motor, detecting as if the cleaning means reached the home position or the other end of the charging wire. Therefore, with the cleaning means locked between the home position and the other end of the charging wire, a copying process is effected by the copying machine to reproduce an image which is defective due to a white patch or line. One solution would be to employ a sensor for detecting unwanted stoppage of the cleaning means between the home position and the other end of the charging wire, indicate a failure, inactivate the copying machine, and energize a serviceman call indicator. This solution is however also disadvantageous in that even when the cleaning means is stopped somewhere in its moving stroke due to a small amount of smear on the cleaning means, the copying machine is shut down and no image can be produced until the cleaning means is repaired by a serviceman. Therefore, the efficiency of forming images in the image forming device is poor.